Separate figures suggest that couples with children and one earner can expect to see the impact of the hikes eased by increases in child benefit and child tax credit.

Mr Darling said yesterday: 'The burden really is falling on people on higher incomes.

'People who have done well over the years are going to pay a bit more.' The Treasury claimed that the national insurance hikes would be offset for those earning between £20,000 and £40,000 by increases in personal income tax allowances.

'Tax bombshell': George Osborne says the mini-Budget is the 'wrong track for Britain'

But the Institute said that relied on a misleading comparison.

Mr Darling's calculations compare the position in 2011 with that in April 2008, before Labour increased personal allowances by £600 to compensate for the scrapping of the 10p tax band.

But the Institute said the sensible starting point should be the system in the current tax year, which already incorporates the increase.

Mike Brewer, of the Institute, said that the Treasury assertion was 'strictly true' if the starting point was April 2008.

But he added: 'The changes are dominated by the changes in National Insurance, which mean that if you earn less than £20,000 a year you are better off and if you earn more than £20,000 a year you are worse off.'

Shadow Chancellor George Osborne said: 'This is independent confirmation of what we have been saying. The giveaways were for Christmas, while the tax rises are for life.'

The Institute also said a squeeze on Whitehall spending would wipe out £37billion planned for front-line spending on schools, hospitals and other public services.

Tory Treasury spokesman Philip Hammond said that scrapping the planned 45 per cent income tax rate 'would not be a priority' for the Conservatives - risking a row with Right-wingers.

'Our first priority must be to protect those on the lowest incomes,' he said.

'Bye. See you in a few years... I hope!'

Our 'gargantuan' interest burden

Britain will be spending more on interest payments alone by 2010 than on schools, it has emerged.

Independent experts and the Tories said Government figures suggested interest payments would hit between £40billion and £50billion a year.

That compares with a projected schools budget of £31.9billion for the same year, a transport budget of £ 14billion and an entire annual defence budget of £ 45.6billion.

According to Monday's figures from the Chancellor, total borrowing will reach £1trillion by 2014 - equivalent to £40,000 per UK household.